The register is built into the cpu, it is used to store temporary data that the cpu needs to access quickly in oder to perform its operation.

Types of cpu registers

• General-purpose registers : These registers can be used to store any type of data, including operands for arithmetic and logic operations, pointers to memory locations, and intermediate results of calculations.

• Program counter register: This register holds the address of the next instruction to be executed by the CPU.

• Stack pointer register: This register holds the address of the top of the stack, which is a region of memory used to store function call frames and temporary data.

• Status registers: *These registers store the state of the CPU, including information about arithmetic operations, interrupt handling, and other control signals.

**

registers

rax" - a large general-purpose register used for storing values and results of arithmetic operations.

"rbx" - another large general-purpose register.

"rcx" - a general-purpose register used for counting and loop operations.

"rdx" - a general-purpose register used for storing values and results of arithmetic operations.

"rsi" - a general-purpose register used as a source index register in string and array operations.

"rdi" - a general-purpose register used as a destination index register in string and array operations.

"r8" - "r15" - additional general-purpose registers available in the x86-64 architecture.

General-purpose registers :: rax, rbx, rcx, rdx, rbp, rsp, rsi, rdi, r8, r9, r10, r11, r12, r13, r14, r15

Operation

ADD- integer add
SUB- subtract
MUL- unsigned multiply
IMUL- signed multiply
DIV- unsigned divide
IDIV- signed divide
INC- increment
DEC- decrement
NEG- negate

CONTROL FLOW JE - jump if equal

JZ - jump if zero

JNE - jump if not equal

JNZ - jump if not zero

JG - jump if the first operand is greater than second

JGE - jump if the first operand is greater or equal to second

JA - the same that JG, but performs an unsigned comparison

JAE - the same that JGE, but performs an unsigned comparison

DATA TYPES byte is eight bits word is two bytes doubleword is four bytes quadword is eight bytes double quadword is sixteen bytes (128 bits).

.DATA +-----------+-------------------+-------------------+ | Directive | Purpose | Storage Space | +-----------+-------------------+-------------------+ | DB | Define Byte | allocates 1 byte | | DW | Define Word | allocates 2 bytes | | DD | Define Doubleword | allocates 4 bytes | | DQ | Define Quadword | allocates 8 bytes | | DT | Define Ten Bytes | allocates 10 byte | +-----------+-------------------+-------------------+

// opertation

mov ebx, 123 ; ebx = 123 mov eax, ebx ; eax = ebx add ebx, ecx ; ebx += ecx sub ebx, edx ; ebx -= edx mul ebx ; eax ***= ebx div edx ; eax /= edx

; eax handles operations

data - section is used for declaring initialized data or constants bss - section is used for declaring non initialized variables text - section is used for code

RESB, RESW, RESD, RESQ, REST, RESO, RESY and RESZ - are used for declaring non initialized variables INCBIN - includes External Binary Files EQU - defines constant.

one equ 1